The invention relates to a method for machining a component or a component array by means of electromagnetic radiation, in which the component or the component array comprises at least two materials disposed in succession in the incident direction of the electromagnetic radiation.
It is well known to use electromagnetic radiation, in particular laser radiation, for joining components. From German Patent Disclosure DE 195 20 336 A1, a method for soldering electronic components onto a circuit substrate is known, in which laser radiation is employed to heat and melt the solder.
Similar methods are also known from German Patent Disclosures DE 40 17 286 A1, DE 40 38 765 A1, and DE 195 29 388 A1.
It is also known to use laser radiation for soldering components of ceramic material to components of metal. The metal is disposed downstream of the ceramic material in the incident direction, and there is a glass solder between the two materials. The laser radiation is aimed at the ceramic material and is partly absorbed by it and partly passed through to the glass solder, disposed downstream of the ceramic material in the incident direction, and to the metal disposed downstream of the glass solder in the incident direction. The absorption of the laser radiation in the ceramic material and in the metal leads to heating of these materials, and as a result the glass solder is also heated and melts. Once the glass solder has melted in the desired way, the laser radiation can be turned off. In the ensuing solidification of the glass solder, this solder bonds the ceramic material to the metal.
One disadvantage of this known method is that a high intensity of the laser radiation is required in order to assure that a sufficient proportion of the laser radiation will be passed through to the metal so that it can be absorbed by it. This entails a high temperature gradient, which leads to thermal stresses and often to cracking in the ceramic body, which destroys the component. For this reason, the known method has proved to be of only limited utility.
One object of the invention is to provide an improved technique for machining a component or a component array.
Another object of the invention is to provide a technique for machining a component or a component array with electromagnetic radiation, which technique is also suitable for joining components.
A further object of the invention is to provide a technique for machining a component or a component array with electromagnetic radiation in which damage to the components is reliably avoided.
The fundamental concept of the teaching according to the invention is to employ electromagnetic radiation of different wavelengths for machining components or component arrays that comprise different materials; at least some of the different materials of the component or the component array are assigned electromagnetic radiation of a wavelength that is absorbed more strongly by the affected material than by the other materials. In this way, selective machining of the various materials is made possible, since the electromagnetic radiation assigned to one material acts predominantly or exclusively on that material.
When components of ceramic material are soldered to components of metal, laser radiation of a first wavelength and second wavelength can for instance be used; the first wavelength is absorbed more weakly by the ceramic material than by the metal. In this way, the absorption of the laser radiation of the first wavelength in the ceramic material is reduced, so that on the one hand adequate absorption by the metal and thus adequate heating of the metal is attained. On the other hand, an undesired absorption of laser radiation of this wavelength by the ceramic material is averted. In this way, the risk of cracking from thermal stresses because of an overly high temperature gradient in the ceramic material, and thus the risk of damage to the component, are reliably avoided.
The method of the invention can be performed simply and quickly and in manifold ways. It is especially well-suited to joining components or component arrays of different materials, for instance for soldering, welding or adhesive bonding of them.
The wavelengths of the electromagnetic radiation can be selected within wide limits to suit the particular materials to be machined. The radiation sources for generating the electromagnetic radiation can likewise be selected within wide limits to suit the applicable requirements and the materials to be machined. Both radiation sources whose electromagnetic radiation has a single wavelength and radiation sources whose electromagnetic radiation has multiple wavelengths can be used. The wavelengths can also be selected such that a material absorbs electromagnetic radiation of a plurality of wavelengths.
An especially advantageous feature of the teaching of the invention provides that the first and the second wavelength are selected such that the electromagnetic radiation of the second wavelength is absorbed by the first material, while the electromagnetic radiation of the first wavelength is passed substantially completely through from the first material to the second material disposed downstream of the first material in the incident direction. In this embodiment, the electromagnetic radiation of the first wavelength is substantially not absorbed by the first material but instead is substantially passed completely through to the second material. In this way, an undesired absorption of the electromagnetic radiation of the first wavelength in the first material is substantially avoided. The electromagnetic radiation of the first wavelength is instead passed through to the second material, in which it is absorbed and acts in the desired way on that material.
In principle, it is possible for the electromagnetic radiation of the first wavelength and the electromagnetic radiation of the second wavelength to be generated by the same radiation source, such as a radiation source that generates electromagnetic radiation in a wavelength band that includes the first wavelength and the second wavelength. An advantageous embodiment, however, provides that the electromagnetic radiation of the first wavelength and the electromagnetic radiation of the second wavelength are generated by different radiation sources. In this embodiment, an adaptation of the various radiation sources to the various materials is made possible; for instance, the intensity of the electromagnetic radiation can be selected for the various materials separately from one another. Furthermore, the action time of the electromagnetic radiation or the type of action, such as continuous or pulsed operation, can be selected for the various materials separately from one another.
Another refinement provides that the electromagnetic radiation of the first wavelength and the electromagnetic radiation of the second wavelength are generated by radiation sources of different types of radiation. The electromagnetic radiation of the first wavelength and the electromagnetic radiation of the second wavelength can, however, also be generated by radiation sources of the same type of radiation, as another refinement provides. In the aforementioned embodiments, laser radiation and/or infrared radiation can for instance be employed as the types of radiation. In the embodiment having the radiation sources of different types of radiation, at least one of the radiation sources can for instance be formed a laser and at least one another radiation source can be formed an infrared radiator. In the embodiment with the radiation sources of the same type of radiation, lasers can for instance be used exclusively as the radiation sources.
The shape, size and geometry of the component or the component array to be machined can be selected within wide limits. One embodiment provides that the second material immediately follows the first material in the incident direction of the electromagnetic radiation. In this embodiment, the two materials are placed adjacent one another, so that they can for instance be welded to one another.
Another refinement provides that at least one third material, which is substantially permeable to the electromagnetic radiation of the first wavelength, is disposed between the first material and the second material. In this embodiment, the electromagnetic radiation of the first wavelength is passed through from the first material to the third material and from there to the second material, so that it acts substantially only on the second material.
The first material can in principle be disposed under the surface of the component, as long as the surface of the component comprises a material that is sufficiently permeable to the electromagnetic radiation of the first and second wavelengths. Expediently, however, the first material forms one surface of the component or the component array. In this embodiment, the electromagnetic radiation directly strikes the first material, and the electromagnetic radiation of the first wavelength is passed partly or completely through to the second material, and the electromagnetic radiation of the second wavelength is absorbed by the first material.
The intensity of the electromagnetic radiation can be selected to suit the applicable requirements, and in the case of different radiation sources can also be selected separately from one another for the radiation of the various wavelengths. An especially advantageous embodiment provides that as a function of the thickness of the first or second material in the incident direction of the electromagnetic radiation, the wavelength and intensity of the electromagnetic radiation are selected such that the electromagnetic radiation of the second wavelength is absorbed substantially completely by the first material and/or the electromagnetic radiation of the first wavelength is absorbed substantially completely by the second material. In this way, the electromagnetic radiation of the second wavelength for instance acts substantially exclusively on the first material, so that an undesired action on the second material or further materials that are disposed downstream of the first material in the incident direction is averted.
An extraordinarily advantageous refinement of the teaching of the invention is that the first material is a ceramic material; that the second material is a metal; and that the third material is a bonding material for bonding the ceramic material to the metal. It has been found that the teaching of the invention is extraordinarily well suited to the joining of components of ceramic material to components of metal.
A refinement of the aforementioned embodiment provides that the third material is a glass solder, which is preferably disposed between the ceramic material and metal or upon heating of the ceramic material and/or of the metal is introduced and in particular flows into the region between the ceramic material and the metal. In this embodiment, the method according to the invention is used to solder components of ceramic material to components of metal by means of a glass solder. By means of the method of the invention, the soldering is made simple and reliable, without the risk that the ceramic material will be damaged. Thus the method of the invention for the first provides a possibility of soldering components of ceramic material to components of metal simply and quickly and substantially independently of the component geometry.
A refinement of the teaching of the invention provides that the electromagnetic radiation of the first wavelength is generated by an Nd:YAG laser or a diode laser or an infrared radiator, and the electromagnetic radiation of the second wavelength is generated by a CO2 laser. This refinement is advantageous particularly in those embodiments in which a component of ceramic material is soldered to a component of metal, since appropriate ceramic materials are substantially permeable to the radiation of an Nd:YAG laser, diode laser or infrared radiator, while they absorb the radiation of a CO2 laser. Another embodiment provides that the component or the component array is embodied rotationally symmetrically, and that in the radial direction from the outside to the inside, the first material and the second material follow one another, and optionally at least one further material, such as the third material, is located between the first material and second material. In this embodiment, the electromagnetic radiation of the first wavelength is passed through from the radially outer layer of the component to a radially inner layer, while the laser radiation of the second wavelength is absorbed by the radially outer layer of the component, In this way, selective machining of rotationally symmetrical components is made possible.
Particularly in the joining of components, it can be sufficient to use electromagnetic radiation of a first wavelength and a second wavelength. If necessary, however, more than two wavelengths can also be used. To that end, one embodiment provides that electromagnetic radiation with three or more wavelengths is used, and that associated with the electromagnetic radiation of each wavelength is a material in the component or the component array which absorbs the electromagnetic radiation of that wavelength more strongly than the electromagnetic radiation of the other wavelengths, while the other materials absorb the electromagnetic radiation of that wavelength more weakly the material associated with that wavelength. In this embodiment, selective machining is made possible even for components or component arrays that comprise three or more materials.
An especially advantageous refinement of the aforementioned embodiment provides that the material associated with the electromagnetic radiation of a wavelength absorbs the electromagnetic radiation of that wavelength, while it is substantially permeable to the electromagnetic radiation of the other wavelengths. In this embodiment, the electromagnetic radiation of one wavelength associated with one material acts substantially exclusively on that material, so that an undesired action on the other materials is avoided.
Another embodiment provides that the electromagnetic radiation of the first wavelength has the electromagnetic radiation of the second wavelength and/or electromagnetic radiation of a further wavelength superimposed on it, in such a way that the electromagnetic radiation of the various wavelengths is aimed from the same direction onto the component or the component array. In this embodiment, the electromagnetic radiation of different wavelengths impinges in the same region on the component or the component array to be machined.
However, the electromagnetic radiation of various wavelengths can also be aimed at the component from various directions, as another embodiment provides.
In principle, it suffices if the various wavelengths are generated by the same radiation source, or if a separate radiation source is provided for each wavelength. A refinement, however, provides that for at least some of the various wavelengths, the electromagnetic radiation is generated by more than one radiation source, or the incident radiation is split into a plurality of split beams. In this embodiment, the electromagnetic radiation of one wavelength can for instance be aimed simultaneously from multiple directions at the component to be machined.
In another embodiment, beam forming means are disposed in the beam path of the incident electromagnetic radiation. This enables shaping of the incident radiation, such as focusing or the forming of a beam spot of a desired shape on the component.
During the machining, the component or the component array and the radiation source or sources can be in repose relative to one another. However, they can also be moved relative to one another during the machining, as another embodiment provides.
The method of the invention is suited in a versatile way for the machining of components or component arrays. An especially advantageous embodiment, however, provides that the component array has a first component, which comprises the first material, and a second component, which comprises the second material, and that the first component is joined to the second component. The method of the invention is especially well suited to such joining methods.
A refinement of the aforementioned embodiment provides that the first component and the second component follow one another directly in the incident direction of the electromagnetic radiation, and that the first component is welded or fused to the second component. In this exemplary embodiment, the electromagnetic radiation of the second wavelength acts on the first component, while the electromagnetic radiation of the first wavelength acts on the second component. Given a suitable choice of intensity and action time of the electromagnetic radiation, the components can be welded or fused to one another in this way.
Another embodiment provides that in the incident direction of the electromagnetic radiation, a solder is located between the first component and the second component, by means of which the first component is soldered to the second component. The solder can be substantially permeable to the electromagnetic radiation of the first wavelength, so that the electromagnetic radiation of the second wavelength heats the first component and the electromagnetic radiation of the first wavelength heats the second component, until the solder melts and the components are thus soldered together.
It is also an object of the invention to provide an apparatus for joining, in particular soldering, a component comprising a first material to a component comprising a second material.
The apparatus of the invention is based on the concept of using electromagnetic radiation with at least two wavelengths for the machining, which are selected such that the radiation of the one wavelength acts predominantly or exclusively on the first component, while the electromagnetic radiation of the other wavelength acts predominantly or exclusively on the second component. For this reason, the apparatus according to the invention is suitable for selective material machining of components and component arrays comprising different materials.
An especially advantageous refinement of the apparatus provides control means, which control the intensity of the electromagnetic radiation of the second wavelength as a function of the thickness of the first material in the incident direction in such a way that the electromagnetic radiation of the second wavelength is absorbed substantially completely by the first material. In this way, an undesired action of the electromagnetic radiation of the second wavelength on the other materials is reliably avoided.